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Fundamentals of MBR design

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The design of a membrane bioreactor system largely relates to:

  • the configuration of the membrane,
  • the membrane separation process, and
  • the biotreatment process.

1. Membrane separation process configuration:

Membrane configuration concerns the geometry of the membrane (hollow fibre, flat sheet or tubular) and the direction in which the water flows through it (in-to-out or out-to-in).

The membrane separation process configuration concerns the placement of the membrane module in the overall MBR process, i.e. either inside or outside the tank.

Figure 1.   Membrane separation process configurations | About Mbrs Simon Judd Design 1
Figure 1. Membrane separation process configurations

2. Biotreatment process configuration:

The biotreatment process configuration determines the biochemistry and, therefore:

  • which pollutants are removed (organic carbonaceous materials, ammoniacal compounds and nutrients), and
  • which products are formed (carbon dioxide or methane, nitrate or nitrogen, etc).

Biotreatment using air is referred to as ‘aerobic treatment’, leading to carbon dioxide as the main carbon-based product. In the absence of air, biotreatment is termed ‘anaerobic treatment’, which yields methane.

Biotreatment processes can be configured either as ‘fixed film’ or ‘suspended growth’. An MBR is a suspended growth process, based on the classical activated sludge (CAS) process but with membrane separation rather than sedimentation of the retained biological solids.

Membrane technology is integrated with a biological process either as a filter for retaining the biomass, as in an MBR, or as a diffuser for introducing air or oxygen in the molecular or bubbleless form, as in a membrane aerated biofilm reactor or MABR.

Membrane filtration may also be used downstream of a CAS for removing residual solids. In this case it is not integrated with the biological process and may be referred to as a 'polishing' step.

Figure 2.  Biotreatment process configurations | About Mbrs Simon Judd Design 2
Figure 2. Biotreatment process configurations

Further elements of design comprise pretreatment (screening and, for some applications, clarification) and post-treatment (generally either disinfection or desalination).


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Hello. I am working in KOLTEK Consulting firm in Turkey/Ankara. Nowadays we have a project and we are planning to use SBR in package wastewater treatment . There will be 13 package treatment. We are looking some alternatives to decrease this valur with that larger package wastewater treatment in a middle of some village wit using MBR in it. I just wondered is there any catalog for MBR in your company. Thank you.

Claire JuddAtakan

Hi Atakan. Please note The MBR Site does not supply equipment. You can contact our advertisers or find suppliers in our MBR directories. You can also post consultancy queries on The MBR Group on


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About this page

'Fundamentals of MBR design' was written by Simon Judd

This page was last updated on 01 June 2021


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